Thermal contact resistance evaluation of a thermoelectric system by means of three I-V curves

Abstract

To achieve a suitable performance in a thermoelectric (TE) device it is important to minimize the thermal contact resistances between the device external surfaces and the heat exchangers of the system (heat source and heat sink). Despite its relevance, there are not many methods available for the evaluation of the thermal contact resistance, and the existing ones typically employ complex setups. Here, we present a new method to determine the thermal contact resistance of a TE device thermally contacted to a heat sink and a heat source. The method is based on performing three current-voltage (I-V) curves at different system conditions under a small temperature difference. First, an I-V curve with a high voltage scan rate, which avoids the variation of the initial temperature difference, provides the ohmic resistance. A second I-V curve performed with a constant input heat power (or the device suspended) provides the TE resistance. Finally, a third I-V curve with a constant temperature difference between the heat exchangers allows obtaining the thermal contact resistance. Using this method, a thermal contact resistivity value of 3.57 × 10−4 m2KW−1 was obtained for a commercial Bi-Te TE module contacted with a heat source and a heat sink using thermal grease as thermal contact interface material, which is in good agreement with reported values. The new method is highly advantageous, since neither involves complex setups nor requires the measurement of heat fluxes. Moreover, it measures directly under operating conditions for small temperature differences.